Resin additives such as phenolic antioxidants, UV absorbers and hindered amine compounds are known to suppress degradation by light or heat of organic materials such as synthetic resins.
As the compounds used as the resin additives, those compounds having a high melting point, low ability to plasticize the resin and small vaporization from the resin, such as tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxymethyl)methane and tris(2,4-di-tertiary butylphenyl)phosphite, are usually preferred. However, when the molecular weight of the compound is too high, the additive cannot move in the resin, so that the stabilizing effect thereof tends to be decreased.
On the other hand, compounds having a low melting point, such as stearyl (3,5-di-tert-butyl-4-hydroxyphenyl) propionate and bis(2,2,6,6-tetramethylpiperidyl) sebacate have a relatively low molecular weight and have an excellent stabilizing effect at an early stage. However, since they are easy to vaporize from the resin, their long term stabilizing effect is poor, and since they are liquid or viscous, or, in case of powdery compounds, they form large lumps due to caking when stored, their handling property is poor. To improve their handling property, it is necessary to make the compounds into the form of a master batch.
However, since usual hindered amine compounds have a low compatibility with polyolefin resins, there is a problem in that the hindered amine compound exude from the surface of the pellets, which results in the caking of the pellets when a master batch containing a high concentration of a hindered amine compound is prepared. Therefore, the hindered amine compounds can be blended to an amount of only about 50 parts by weight per 100 parts by weight of a polyolefin, so that the merit to make the composition into the form of a master batch is small.
Especially, while the hindered amine compounds obtained by reacting 2,2,6,6-tetramethylpiperidinols with a fatty acid have an excellent weatherability-imparting effect, they have a low molecular weight and are likely to be liquefied. When they are made into a master batch with a resin in order to improve their handling property, since the additive exudes from the surface of the resin composition made into the form of a master batch and shows adhesiveness, it is necessary for the master batch to have a low concentration. There is also a problem in that when the concentration is high, the strength of the composition during the production of the master batch is low, so that pellets cannot be produced stably and continuously.
As the methods for improving the handling property or the like of the additives, for example, a method in which the tackiness is suppressed by making the master batch using an oil-absorbing polymer (Patent Document 1); a method in which the composition is made into a master batch having a core layer and a sheath layer to prevent the breakage of strands (Patent Document 2); a method in which the composition is made into microcapsules (Patent Document 3); and a method in which the powder characteristics are improved by enhancing the crystallization of a low melting flame retardant (Patent Document 4) have been proposed. All of these are techniques improving the ease of handling of liquid and low melting additives.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 9-52956 (Claims)    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2000-80172 (Claims)    Patent Document 3: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 10-512320 (Claims)    Patent Document 4: Japanese Unexamined Patent Application Publication No. 9-87290 (Claims)